1. Field of Invention
This invention relates to a method of producing a worked shaft by stretching the shaft to reduce its diameter, moving a component onto the stretched shaft, and terminating the stretching so that the shaft regains some of its original diameter and secures the component to the shaft. In particular, this invention relates to a method of producing worked camshafts.
2. Description of the Prior Art
To attach cams or other components to a camshaft, which is hollow in a manner that has long-term stability, it is known that prefabricated cams or components may be pushed onto the camshaft and to widen them hydraulically in some locations so that the cams and/or components are secured in a torsionally fixed manner. The locally limited widening of the camshaft is relatively complex because special provisions are required (special probes, seals, etc.).
U.S. Pat. No. 5,299,881 describes a worked camshaft in which the individual cams and the corresponding camshaft are first manufactured completely in separate manufacturing steps and then the cams are pushed onto the camshaft using a special joining technique so that there is a fit without play between the shaft and the cams. The prefabricated cams each have an inside bore and at least two annular zones spaced a distance apart axially, separated by at least one free space which is in the inside bore of the cams. The space and the zones are arranged symmetrically with the center plane of the cams. To manufacture the worked camshaft, the individual cams are pushed onto the camshaft in such a way that a fit is obtained between said zones and the circumference of the shaft. There is a problem inasmuch as it is relatively difficult and problematic to attach said shafts, in particular when the shafts are pushed onto or over the regions to which they are to be secured. Furthermore, the cams have a relatively complex design and therefore may be manufactured only at a comparatively high cost. SUMMARY OF THE INVENTION
The object of the present invention is to create a method of manufacturing a worked shaft in which the mounting of cams and/or other components on the shaft can be accomplished relatively easily and inexpensively.
This object is achieved by a method of manufacturing a worked shaft that includes placing at least one component to be mounted on a shaft on a first portion of the shaft, the component having an inner opening with an inside diameter, and stretching the shaft such that in at least one shaft mounting site on a second portion of the shaft an original diameter is reduced to a stretched diameter that is larger than the component inside diameter. The method includes moving the component onto the second portion of the shaft and displacing the component to the mounting site by applying a force, and terminating the stretching such that the stretched diameter enlarges in a direction of the original diameter so as to secure the component to the shaft.
The essential advantage of the present invention is that complex hydraulic widening operations on a hollow shaft, in particular a camshaft such as those required in the related art need not be performed because the diameter of the shaft is reduced elastically by stretching before pushing the cams and/or other components onto the shaft, so that it is readily possible to push said cams and/or components onto the shaft. Advantageously, no complex changes need be made on the cams and/or components themselves in the implementation of the method according to this invention.